Marking instrument



FIG. 1 is an exploded perspective view of a marking instrument showing our new design;

FIG. 2 is a perspective view thereof with the cap affixed;

FIG. 3 is a front elevational view, the rear elevational view being a mirror image thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof; and

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a marking instrument, as shown and described. 